Threshold-based alert evaluation for Monitorex.

Runs during the Collector cleanup cycle and fires notifiers when metrics exceed configured thresholds. Debounce prevents repeated alerts within a configurable min_interval.

Configuration

config :monitorex, :alerts, [
  %{
    name: "High error rate",
    metric: :error_rate,
    op: :gt,
    threshold: 0.05,
    window_seconds: 300,
    min_interval_seconds: 300,
    notifiers: [webhook: "https://hooks.example.com/alerts"]
  }
]

Supported metrics

• :error_rate — host-level error rate (errors / requests, float 0.0–1.0)
• :avg_latency_ms — host-level average latency in ms
• :p99_latency_ms — host-level p99 latency in ms
• :requests_per_min — host-level request rate
• :host_down — no events from a host for window_seconds

Supported operators

• :gt — greater than threshold
• :lt — less than threshold